UL’s testing process involves placing test assemblies in a furnace and exposing one face to fire to determine the fire rating. In the case of glass assemblies (shown here), the fire is evident during the testing process.

In the case of opaque assemblies, the testers must rely more on temperatures collected by thermocouples inside the furnace. After the test fire is extinguished, UL technicians can compile the temperature data, along with information such as roof-deck deformation (shown here) and material failure to help determine the rating (in hours) that each assembly receives.

A model code such as the IBC has no legal standing until it is adopted as law by a legislative body. This is done at the local level by a state legislature, county board, or city council. Sometimes the federal government will mandate certain code requirements. (For example, codes may be mandated in order to secure Medicare and Medicaid financing for a healthcare facility.) While legislative bodies are not compelled to adopt model building-safety or fire-prevention codes, at the moment, all 50 states and the District of Columbia have adopted the IBC. Nonetheless, sometimes local governments will draft their own amendments—as California is known to do—though the practice is discouraged. While the main goal of the IBC is to establish the minimum requirements necessary to provide safety, guard public health, and reduce property losses, it also manages to keep construction costs down. It does so by encouraging uniformity in the construction industry, allowing building and material manufacturers to do business at a larger scale that leads to reductions in cost. Excessive amendments to the model code erode this uniformity.

When adopted as law, all owners of property within the boundaries of the adopting jurisdiction are required to comply with the codes. Since codes are updated regularly, an existing structure need only meet the code that was enforced when it was built. However, reconstruction, rehabilitation, or alteration of the existing structure, or a change in occupancy as defined by the building code, all require that the structure be brought up to date to meet the most current version. There are exceptions: Certain code revisions are deemed essential to life safety and can require retroactive provisions for existing buildings. While the ICC updates the IBC every three years, it is not always immediately adopted by every legislative body. In fact, there are some states that are still using the 2000 version of the code.

There are chapters in the IBC that relate to fire alarms, sprinklers, ingress and egress, and other life-safety measures related to a possible fire event, but it is chapters five, six, and seven that pertain specifically to fire-resistive-rated construction. “Our code tells you how big you can build depending on occupancy and type of construction,” Reeves says. “The point is, the more fire resistance you put into a building, the bigger you can build. For example, a Type IIB building, which is light non-combustible construction with no fire protection on the main structure, allows you 23,000 square feet per floor. If you build a IIA, which is the same type of construction but with one-hour protective ratings on all structural members, you can increase that to 37,500 square feet per floor.”

Testing and Fire Rating

The building code mandates the type of construction for the desired building height, number of stories above grade, floor area per story, and occupancy group—the requirements of fire performance and continuity—but is silent in terms of the actual materials and assemblies that make up the fire-resistive construction. To find systems that meet the code’s requirements, architects must often refer to manufacturers’ specifications. Manufacturers, in turn, get their products rated by approved testing laboratories, including Nationally Recognized Testing Laboratories (NRTLs). NRTLs are private-sector organizations that the Occupational Safety & Health Administration (OSHA) has deemed capable of determining whether products meet consensus-based standards. There are 16 NRTLs currently recognized by OSHA that test and approve everything from toasters to solar panels. The largest of these, and one of the few with the equipment necessary to fire-rate building assemblies, is Underwriters Laboratories (UL).

UL uses “Fire Tests of Building Construction and Materials,” also known as ANSI/UL 263. The standard spells out the procedure to determine the hourly fire rating of a construction assembly. “Typically, material manufacturers will contract with our agency to run the test,” UL’s Walke says. “They determine the materials and design the assembly—say they want to use type XYZ gypsum over wood studs with certain fastening tips. We then construct the assembly according to their specifications and run the test.”